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    Subject[PATCH 06/30] soc: bcm: brcmstb: Document panic notifier action and remove useless header
    Date
    The panic notifier of this driver is very simple code-wise, just a memory
    write to a special position with some numeric code. But this is not clear
    from the semantic point-of-view, and there is no public documentation
    about that either.

    After discussing this in the mailing-lists [0] and having Florian explained
    it very well, this patch just document that in the code for the future
    generations asking the same questions. Also, it removes a useless header.

    [0] https://lore.kernel.org/lkml/781cafb0-8d06-8b56-907a-5175c2da196a@gmail.com

    Fixes: 0b741b8234c8 ("soc: bcm: brcmstb: Add support for S2/S3/S5 suspend states (ARM)")
    Cc: Brian Norris <computersforpeace@gmail.com>
    Cc: Doug Berger <opendmb@gmail.com>
    Cc: Florian Fainelli <f.fainelli@gmail.com>
    Cc: Justin Chen <justinpopo6@gmail.com>
    Cc: Lee Jones <lee.jones@linaro.org>
    Cc: Markus Mayer <mmayer@broadcom.com>
    Signed-off-by: Guilherme G. Piccoli <gpiccoli@igalia.com>
    ---
    drivers/soc/bcm/brcmstb/pm/pm-arm.c | 16 ++++++++++++++--
    1 file changed, 14 insertions(+), 2 deletions(-)

    diff --git a/drivers/soc/bcm/brcmstb/pm/pm-arm.c b/drivers/soc/bcm/brcmstb/pm/pm-arm.c
    index 3cbb165d6e30..870686ae042b 100644
    --- a/drivers/soc/bcm/brcmstb/pm/pm-arm.c
    +++ b/drivers/soc/bcm/brcmstb/pm/pm-arm.c
    @@ -25,7 +25,6 @@
    #include <linux/kernel.h>
    #include <linux/memblock.h>
    #include <linux/module.h>
    -#include <linux/notifier.h>
    #include <linux/of.h>
    #include <linux/of_address.h>
    #include <linux/panic_notifier.h>
    @@ -664,7 +663,20 @@ static void __iomem *brcmstb_ioremap_match(const struct of_device_id *matches,

    return of_io_request_and_map(dn, index, dn->full_name);
    }
    -
    +/*
    + * The AON is a small domain in the SoC that can retain its state across
    + * various system wide sleep states and specific reset conditions; the
    + * AON DATA RAM is a small RAM of a few words (< 1KB) which can store
    + * persistent information across such events.
    + *
    + * The purpose of the below panic notifier is to help with notifying
    + * the bootloader that a panic occurred and so that it should try its
    + * best to preserve the DRAM contents holding that buffer for recovery
    + * by the kernel as opposed to wiping out DRAM clean again.
    + *
    + * Reference: comment from Florian Fainelli, at
    + * https://lore.kernel.org/lkml/781cafb0-8d06-8b56-907a-5175c2da196a@gmail.com
    + */
    static int brcmstb_pm_panic_notify(struct notifier_block *nb,
    unsigned long action, void *data)
    {
    --
    2.36.0
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